Many industrial and commercial electronic article surveillance applications make use of a radio frequency transponder for detecting and identifying an article of interest. A typical radio frequency (RF) transponder for use in such applications comprises an antenna coupled to an electronic circuit carried on a substrate. In response to an interrogation signal received by the antenna, the electronic circuit generates a response transmitted by the antenna for receipt at a base station. The presence and characteristics of the response signal indicate the presence and nature, respectively, of the article that carries the RF transponder.
RF transponders of the type described above have proliferated in the retail environment for use in theft detection. Many different types of articles presently carry a transponder circuit which a store clerk will deactivate after purchase by the customer. However, should someone try and remove steal the article without purchase (and deactivation of the transponder), the transponder on the article will respond to a signal from a theft detection system. The response from the RF transponder on the article causes the theft detection system to generate an alarm so that store security can apprehend the would-be thief before leaving the store. Because of the effectiveness of RF transponders for theft detection, many large retailers now require their vendors to provide such transponders on articles for sale.
Presently, RF transponders of the type used for article surveillance exist in various forms. One popular type of transponder comprises an adhesive tag that includes the antenna and circuit in a single package for adhering to an article. Other arrangements include a separate antenna, usually in the form of a thin conductive Mylar® film glued or otherwise attached to the article, for connection to a small semiconductor chip containing the transponder circuit. Unfortunately, RF transponders of the type currently available are not well suited for certain kinds of articles, especially CD and DVD discs. Adhesive tag-type RF transponder circuits, when attached to the top surface of a CD or DVD disc can upset the overall disc balance during use. Moreover, placing an adhesive tag-type RF transponder on the top surface of a disc will detract from the artwork printed on the disc. Also, placing this type of RF transponder on the top surface of a CD or DVD so as to be entirely visible readily increases the likelihood that a would-be thief will attempt to disable the RF transponder to facilitate disc theft.
Another type of RF transponder currently marketed for use with CD and DVDs consists of a pair of half-circular conductive Mylar® arcs glued to the periphery of the disc for attachment at opposing ends to a chip containing a transponder circuit. This arrangement suffers from several disadvantages. First, the cost of this type of RF transponder relative to the cost of the manufacture of the disc is significant, making this type of transponder expensive, if not cost prohibitive. Second, applying each of the Mylar® arcs to the disc will likely prove difficult in a conventional disc manufacturing environment.
Thus, there is need for a RF transponder especially suited for use on a disc such as a DVD or CD.